Messages

1661

General Mach Discussion / Homing Probem

« on: August 23, 2008, 07:35:53 PM »

For some reason I cannot explain, I started having a problem with homing today.  Most of the time, it works correctly, but several times today it would start to home the Y axis, and as soon as it hits the home/limit switch, it stops, flags the limit switch triggered, and stops dead in its tracks.  When I try to manually clear the limit error and back out, I can clear the error, but the instant I hit reset, it re-asserts the limit error, and I am unable to back off the limit.  I could find nothing to get me going again other than killing and re-starting Mach3, whereupon it works correctly.  When Mach3 comes up the second time, it flags "Driver Watchdog Triggered".  It seems like something in Mach3 is getting whacked, because even if I power down the servos and manually back off the limit, it will just do the same thing again until I restart Mach3.
Why is this happening, and why did it just start today?  It's been working correctly for several weeks, and I've changed nothing in Mach or the limit/home hardware.  I have one set of switches, wired in series, for both home and limit on both X and Y.  It happened to me at least 6 times today.

Regards,
Ray L.

1662

General Mach Discussion / Re: closing the loop in mach?

« on: August 22, 2008, 12:49:22 PM »

Kibibble
The motors are strong enough, and I am not over driving them. The problem for me is the controller, and signal. Both of which are crappy. I am looking at a smooth stepper to fix one of those problems. Geckos to solve the rest. But even then, I can still miss steps.
DingbatCA

The you really need to get a better driver and/or clean up the signals!  If your current drivers are not getting a good signal, or you current drivers don't respond reliably, then nothing is going to fix the problem, short of cleaning up the signal, and getting better drivers.  Putting a kludge into the system to deal with one or more pieces of crappy hardware is a lousy solution, and I doubt very much it'll work anyway.  Buy Geckos.  For $100 you'll have the best stepper driver on the market, and your problems will completely go away.
If the brakes on your car only worked intermittently, would you fix them, or put a second set of brakes on to do the job when the first ones don't work?

Regards,
Ray L.

1663

General Mach Discussion / Re: closing the loop in mach?

« on: August 22, 2008, 10:14:27 AM »

I fail to see how closing the loop on a stepper-based system would be of any real value.  The *only* way a stepper will lose position is if you attempt to drive it beyond its capability - either accelerating too fast, or exceeding it's torque capability.  Once that's happened, how would you get it back to the correct position?  The speed will be down, so you need to accelerate, which will exacerbate the problem.  So, how are you going to "catch up"?  With steppers, you must make sure you *never* exceed its capabilities.  If you do that, then they never lose position.  Your real problem is either your motors are too small, or you're driving them too hard.

Regards,
Ray L.

1664

General Mach Discussion / Re: Start and stop spindle from mach 3

« on: August 22, 2008, 12:49:40 AM »

If your motor is not variable speed, just use one of the relay outputs on the C11 to switch the 240V power to the motor controller.  Stopping the program if the motor stops would require some means of detecting that the motor was actually running.  What would cause the motor to stop anyway?

Regards,
Ray L.

1665

Brains Development / Re: mach brain help

« on: August 20, 2008, 10:51:49 PM »

Have a look at the videos on brains in the support tab at top of page, video tutorials.

Brett

Brett,

    Been there, done that, but they cover only the very basics.  It's enough to do the very simplest brains, but no more.  And it's not at all clear what many of the inputs/outputs/button presses/etc. actually do.  Many certainly don't do what their names (in Brain Editor) suggests.  For instance I posted several questions several days ago, and got no responses that addressed the actual questions.  I think this is a very useful bit of functionality, but the lack of any detailed information on how it works, and how to do more than the most basic operations, makes it very difficult to use.

Regards,
Ray L.

1666

Brains Development / Re: mach brain help

« on: August 20, 2008, 10:15:10 PM »

Could you use your brain to generate a feed hold until the arc is ready? 

Don't think you'll get much help here - doesn't seem to be much traffic....  Or perhaps everyone else is just as confused about brains as I am.  What I wouldnt' give for some meaningful documentation.

Regards,
Ray L.

1667

General Mach Discussion / Re: Difference between STEP and DIR

« on: August 20, 2008, 10:33:20 AM »

The signals without BOB C11 were perfect and do not have the problem with the loss of 1 pulse of STEP.
I have 2 more C11 V.2.0, I will make the test with these
The C11 V. 3.1 did not work.
I explain the case to Duncan.
Again thanks for your help.
I'm still starting with the MACH3.
My new experiment will be with Smooth S.
I hope good results, if possible the help you also.

Thank you.

Prendice

Predice,

    CNC4PC C11 v2.0 is exactly the board I had that had this kind of problem.  Definitely get in touch with Arturo, I think he'll fix you up.

Regards,
Ray L.

1668

General Mach Discussion / Re: Difference between STEP and DIR

« on: August 20, 2008, 10:31:06 AM »

I would look at the DIR/STEP timing as it comes out of the PC, and also as it goes into the servo drivers.  It's possible the CNC4PC board is changing the timing.  I do know some of the older CNC4PC boards (At least the C11, not sure about the C11G) used very slow optos for the DIR signals, and fast ones for STEP, which could cause exactly what you're seeing.  In my case, the DIR transitions were delayed 30-60 uSec.  I was able to correct this by changing the phototransitor bias resistors on the board, from 10K to 390 ohms.  The newer CNC4PC boards use the fast optos for all signals.  I suggest you contact Arturo at CNC4PC, and let him know about your problem.  He's very good about customer support.  In my case, he immediately shipped me, at no charge, a brand-new, latest rev board to replace mine, even though it was more than two years old.  The new board works perfectly.

Regards,
Ray L.

1669

Brains Development / Re: Suffering From Brain Damage....

« on: August 19, 2008, 02:53:41 PM »

OK, so that was a total disaster.  Locked the machine up solid, again.  I think I'm starting to understand how these things work, and it seems rather limiting, if I'm right.  Each "lobe" get evaluated any time *any* input changes.  If the result of the evaluation is true, then that is passed on to the next lobe.  What's got me stumped is how to effect changes that cause, directly or indirectly, an input to the brain that initiated the change.  This causes a loop, which locks up Mach3.  Also, I'd like to know how, if possible, to pass through a value, from a DRO etc., which is enabled by a logic condition.  For example, what I'm really trying to do here is look at the current value of Jog%DRO, decide what I want the new value to be, and set that.  But, doing that creates a loop, as Jog%DRO is both an input and an output to/from the same brain.  I've yet to find a way to make this work.  I suspect the "latch" lobe may help here, but I can't figure out what it does, or how to use it.  Seems like it could be used to "hold" an input value, to prevent it from changing while the brain is active, so the brain won't see the updated value it just wrote to the output/DRO/whatever.
Brains would be a helluva lot more useful if there were some documention that explains how they really work.  Having to figure it out by experimentation is very frustrating, and time-consuming.

Regards,
Ray L.

1670

Brains Development / Re: Low Spindle Speed limit

« on: August 19, 2008, 10:21:35 AM »

Gaston,
    I"m hardly an expert, having created my first brain yesterday, but I would expect you'd want a brain that monitored the spindle RPM DRO, and whether the spindle is running.  Test the spindle RPM, and, if too low, force the program to stop, by sending either a Program Stop or E-Stop button press.  I wouild think you could use the "Spindle is Running LED" to know that the spindle is on.  You'll also want a delay on the Spindle is Running LED input, to prevent the brain from executing before the spindle has come up to speed.

Regards,
Ray L.